Mechanism for controlling blade movements of aircraft sustaining rotors



June 2, 1953 H. s. CAMPBELL 2,640,554

MECHANISM FOR CONTROLLING BLADE MOVEMENTS OF AIRCRAFT SUSTAINING ROTORS Myfw June 2, 1953 H. s. CAMPBELL 2,640,554

MECHANISM FOR CONTROLLING BLADE MOVEMENTS 0F AIRCRAFT SUSTAINING ROTORS Filed Oct. l0, 1946 2 Sheets-Sheet 2 Patented June 2, .P1953 MECHANISM FOR 'CGNTROLLIN G BLADE MOVEMENTS F AIRCRAFT 'SUSTAIN- ING ROTORS Harris S. Campbell, Bryn Athyn, Pa., assigner to Autogiro Company of America, Philadelphia, Pa., a corporation of Delaware Application October 10, 1946, Serial No. 702,524

Claims.

This invention relates to a mechanism for controlling the movements of pivoted blades of aircraft sustaining rotors. The present application is a continuation in part of my copending application Serial No. 695,577, filed July 17, 1945, now issued as Patent No. 2,580,514 on January 1, 1952.

Although Various features of the invention are applicable to rotative winged aircraft of a variety of types, the invention is especially concerned With that type of rotative Winged aircraft incorporating a sustaining rotor adapted alternatively to be power driven or to be autorotationally actuated. The invention is especially concerned with a novel blade movement control mechanism effective to control lag-lead displace- `ments of the blades about drag pivot axes.

One of the principal objects of the invention is the provision of a mechanism for controlling differential lag-head displacements as between blades, the mechanism being substantially ineffective with reference to conjoint lagging or leading displacements of all blades in the same sense.

According to another aspect of the invention, the rotor blades are mounted not only on drag pivots but also on flapping pivots, the axes of these two pivots for each blade substantially intersecting each other, but the drag pivots being operatively interposed between the rotor hub and the flapping pivots for the respective blades. the arrangement of the invention the blade movementcontrol mechanism is connected with blade mounting parts which are movable with the blade in the lag-lead sense, with the result that flapping movements are not communicated to the blade movement control mechanism. Because of this conguration of pivots and of the damper mechanism, the latter need not incorporate exible joints or the like which would otherwise be required to accommodate individual flapping movements of the blades.

A still further object of the invention is the provision of a novel form of blade damper.

How the foregoing and other objects and advantages are attained will appear more fully from the following description referring to the accompanying drawings, in which- Figure 1 is a plan outline view of a single rotor helicopter incorporating the mechanism of the present invention, one of the three blades of the sustaining rotor being broken 01T;

Figure 2 is a vertical sectional view, to an enlarged scale, of the rotor head and certain associated parts, this View being taken as indicate by the section line 2 2 on Figure 3;

Figure 3 is a plan view, partly in elevation and partly in horizontal section, of the rotor head shown in Figure 2; and

Figurei is a sectional view of a portion of one of the blade movement control devices.

In considering the drawings attention is first directed to Figure 1 in which the invention is shown as applied to a helicopter type aircraft having a single generally centralized sustaining rotor incorporating three sustaining rotor blades 5 and also having a torque counteracting tail rotor incorporating a pair of blades 6. The rotor and the airscrew are both adapted to be driven by an engine (not shown), and the power transmission is preferably arranged to provide not only for power drive of the rotor and airscrew but also for autorotational actuation of the rotor, for instance in the event of engine failure. These parts need not be described in detail herein since they form no part of the present invention per se. It is noted, however, that they are more fully illustrated and described in my copending application above referred to. It is here further noted that, as disclosed in said copending application, the power transmission desirably includes an overrunning clutch providing for free autorotational actuation of the rotor in the event of engine failure, which clutch is so located in the power transmission that, in the event of engine failure, the torque counteracting airscrew will be driven by the sustaining rotor and therefore will continue its rotation.

Referring now to Figures 2 and 3, the rotor drive spindle 'i which serves also to support the rotor is mounted by means of bearings, one of which appears at S, within a non-rotative supporting sleeve 9 which is adapted to be mounted in the body of the aircraft. At its upper end the spindle 'I is forked as at Ia-1a, the forks being apertured to cooperate with a universal joint I 0 by means of which the rotor hub member II is mounted for tilting movement.

In the illustrated embodiment, with three blades, the hub member I I isl provided with three projecting blade mounting stubs I2 equally spaced angularly about the hub. Each blade is connected with one of the stubs I2 by means of individual pivots which are now described with reference to the blade at the right-hand side of Figures 2 and 3. The root end I3 of the blade is enlarged inwardly to form the external part I4 of a pitch mounting. This part is mounted by bearings I5 and I6 on a spindle I1, the axis of the bearings I5 and IG being substantially coinement` with the iongitudinai axis of the blade or its spar. The bladev is thus `mounted Vwith freedom for pitch change movement, i. e., pivot connections providing for relative angling in one plane but not necessarily any universal motion. Such connections (as seen in Figs. 2 and 3) may comprise apertures 25a, in said levers 25, pinconnccted with the dempers as by pivot pins 2te', and 21a. The spindle 'l is provided with fork prongs itl-48, these prongs being apertured to receive the flapping pivot pin i9, which pin projects transversely through the drag pivot pin 2li which is journaled in apertured ears 2l-2l formed at the outer end of the blade mounting stub i2. The intersecting flapping and drag pivots provide freedom for swinging movement of the blade in the napping sense (as indicated by the lines f--f in Figure 2) and also freedom for lag-lead movement (as indicated by lines l-l in Figure 3). Limiting stops for these blade movements are associated with the intersecting pivots and include a stop member 22 projecting into the interior of the spindle il and serving to denne the range of napping movement f-,. Stop 23 (see particularly Figure 3) projects radially inwardly toward the hub Within the hollow stub l2 and serves to denne the limit of lag-lead motion in the lagging sense. Stop 24 limits swinging of the blade on the drag pivot in the leading sense, the stops 23 and 24 being arranged to define the range of lag-lead movement.

lt will be understood that the blade swinging movements described just above take place with reference to the hub member and thus that the napping and lag-lead movements are movements in addition to the freedom of motion proi vided by virtue of the universal or tilting mounting of the hub member. In Figure 2 a typical range of tilting movement oi the hub is indicated by the lines t--t.

[is seen in Figures 2 and 3, a double-ended lever 25--25 is mounted on and splined to each of the pivot pins 22. Adjacent arms '25 oi adjacent blades are linked together by means oi' a blade movement control device advantageously in the form of a pair of relatively telescoping elements 2li-21. Resistance to -relative movement of the elements 2@ and 2'! is provided `by hydraulic means described below.

lin considering the blade damper arrangement it should be noted that the direct interconnection of the actuating arms 25 around the hub provides for damping lag-lead movements of the blades with relation to each other, without, however, appreciably resisting conjoint lag or lead movement of all blades in the same sense to the same degree. Moreover, since the drag pivots for the blades are operatively interposed between the napping pivots and the hub, and since the dampers operate through levers 25 connected with the drag pivots, flapping motions ci the blades are not communicated to the damper system, and simple pivot connections are all that is needed between the dampers and the levers 25.

Pitch control mechanism is also incorporated in the hub, including pitch control arms 23 projecting from the root ends of the blades, these arms being coupled by means of links 29 to arms 3% which radiate from the rotatable swash member 35. This pitch control mechanism need not be considered in detail herein since it forms no part of the present invention per se and is ully .described in my copending applications above identied.

Turning now to the construction of the blade dempers 2li-2l, as shown at the left hand side oi Figure 3, the parts 225 and 2l constitute piston and cylinder elements adapted to contain a hydraulic damping liquid, for instance oil. A piston 3l (shown in detail in Figure ll) is arranged for relative movement in member 26. This piston 3l is connected by means of a rod 32 with the base end of the external damper member 2i. Therefore, as member 26 telescopes into member 2l, the piston 3i enters farther into the interior of member 2S. This motion of piston 3! into member 2t is resisted or retarded by virtue of the provision of only a small port through the piston, i. e., the port provided at 33 (see Figure fi). The piston 3l also has another passage extended therethrough as indicated at 3Q, and this passage is provided with a ball or similar check valve 35 which is held to its seat by the damping liquid when the piston 3i moves into the member 2t. However, provision is made for relief of presure ahead of piston 3l in the event oi sudden and excessive 'force tending to move the piston into the member 25. This is accomplished by arranging the ball valve 35 in a movable valve member which is normally retained against its seat by a spring 3l. Upon displacement of the member 3S (to the left when viewed as in Figure 4) the cross sectional flow area through the piston is increased, thereby avoiding the build-up of an excessive pressure within member Motion of piston 3l out of member 26 is not subject to appreciable hydraulic resistance, since motion in this direction Will result in opening of the ball valve 35.

As seen in Figure 3, a piston 33 is arranged within the damper member 2l, being spring pressed by means of spring 3s, this piston 3l! serving to maintain a slight pressure on the damper duid to ensure that the pressure chamber will always be nlled. This spring loaded piston further allows the volume of the chamber in member 2l' to vary according to the extent to which the member 26 is telescoped within member 2l, the variable volume being necessary because of the diiierence in cross sectional area of the cavities in the two members 26 and 2l.

With dampers arranged as described above, each individual damper is elfective to resist blade displacements only when a force is transmitted to the damper tending to telescope member 2t into the member 2. With the dampers arranged between and connected with adjacent blades all the way around the hub, the damping action provided is effective to restrain any laglead movements causing the blades to assume out-of-pattern positions. On the other hand, where all blades swing either forwardly or rearwardly in the same direction and to the same extent, no appreciably damping action is provided. In this way variations in the mean angle of lag ci the blades (caused, for example, by a variation in the torque applied to the rotor drive spindle) are not appreciably resisted by the dampers.

It is also of importance in the arrangement above described that the dampers are connected with the drag pivots and that the flapping pivots are operatively interposed between the drag pivots and the blades. Because of this, flapping motions of the blades are not communicated to the damper system and therefore no flexible joints or mechanism need be incorporated to accommodate blade flapping movements.

I claim:

1. For an aircraft sustaining rotor having a hub and a plurality of blades each being connected with said hub through a drag pivot positioned with its axis extended generally transverse the mean plane of blade rotation, mechanism for controlling lag-lead blade movements comprising an operating arm fixed to each blade to move therewith in the lag-lead sense, and damper devices for controlling lag-lead movement of one blade with respect to another, said damper devices comprising pairs of relatively reciprocable members and means for resisting relative movement of said members, one of said members of each pair being connected with the operating arm of one blade and the other member of said pair being connected with the operating arm of another blade, the connection with the arms comprising pivots, and the two members of such pair being arranged for reciprocating movement on an axis extended between arms and acting to impose restraint on relative lag-lead blade displacements.

2. A multibladed aircraft sustaining rotor incorporating a rotative axis member, pivot mechanism mounting the blades on the axis member including flapping pivot means providing for differential lift compensation, the pivot mechanism further including drag pivots providing for lag-lead movements of one blade with respect to another, and interconnections between the blades, the flapping pivot means, the drag pivots and the axis member providing for dierential lift compensation without altering the angular relation between the drag pivot axes, each blade having an operating arm connected with the blade to move therewith in the laglead sense, and damper devices for controlling the lag-lead movement of one blade with respect to another, said damper devices comprising pairs of relatively recipro-cable members and means for resisting relative movement of said members, one of said members of each pair being connected with the operating arm of one blade and the other member of said pair being connected with the operating arm of another blade, the connections with the arms being simple pivots, and the two members of such pair being arranged for reciprocating movement on an axis extended between arms and acting to impose restraint on relative lag-lead blade displacements.

3. For an aircraft sustaining rotor having a hub and a plurality of blades each provided with a flapping pivot, a drag pivot for each blade operatively interposed between the flapping pivot a-nd the rotor hub, and arranged to oscillate with the blades during lag-lead movement thereof, and mechanism for controlling lag-lead blade movements comprising arms connected with the drag pivots to move therewith, and damper devices connected with and extended between arms of adjacent blades around the hub.

4. A construction in accordance with claim 3 in which each damper device comprises a pair of iiuid pressure piston and cylinder devices, one of which is connected with the arm extended from the drag pivot of one blade and the other of which is connected with the arm extended from the drag pivot of an adjacent blade.

5. A construction in accordance with claim 3 in which each damper device comprises a pair of uid pressure piston and cylinder elements arranged to resist relative movement in one direction but to permit relatively free movement in the opposite direction.

HARRIS S. CAMPBELL.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,859,584 Cierva May 24, 1932 1,884,905 Stanley Oct. 25, 1932 1,899,096 Larsen Feb.l 28, 1933 1,905,776 Wilford April 25, 1933 1,948,457v Larsen Feb. 20, 1934 1,971,016 Pecker Aug. 21, 1934 1,971,043 Larsen Aug. 21, 1934 2,217,106 Focke Oct. 8, 1940 2,250,826 Everts July 29, 1941 2,465,681 Gluhare Mar. 29, 1949 

